The Cleveland Cavaliers look slow, old, and have lost eight of their last 10 games. Most worrisome: For the first time in his career, LeBron is noticeably worse on the second night of back-to-backs.

As LeBron James rumbles through his 15th season as an NBA phenom, with enough outward dominance to fill seven-year veterans smack dab in the center of their prime with envy, something feels slightly off.

At 33 years old, James remains the best player in the world and an MVP candidate, averaging his most points since 2010, with the third-highest True Shooting percentage and best assist rate of his Hall-of-Fame career. Compare his arc to others who're this deep into their journey, and those numbers are obscene.

But two qualities that have long separated James from every other player in the universe just aren't there this year. The first is simple: LeBron's presence is the tide that raises all boats. His teams have been dramatically better with him on the court since he was 19 years old, a byproduct of his ability to imprint unparalleled intellect and force onto every possession.

This year, primarily thanks to the roster not executing a defensive scheme that doesn't even suit its personnel, Cleveland is not only barely outscoring opponents with James on the floor, they’re also microscopically better (again: on defense and in tiny segments of every game that are against opposing bench units) when he sits.

It’s impossible to blame LeBron for any or all of this disparity. The talent around him hasn’t been this feeble in eight years. But a closer look at that second separating factor is more interesting.

Photo by Brad Rempel-USA TODAY Sports

James is Hercules. Not only is he bigger, faster, and stronger than whoever’s trying to guard him, but as his opponent begins to tire, the four-time MVP has enough endurance to shift into ninth gear. He doesn’t know what the word exhausted means, or how slowly rising to his feet when a referee's 10 count reaches eight even feels. Stamina is his second wife.

But so far this season, admittedly in a small sample-size, we might finally be witnessing LeBron in his most vulnerable state. This isn’t to say he’s struggling or inferior to anyone who shares the court when he's on it. Everything is relative, and the only standard he's failed to meet is the ostensibly impossible one that he himself has set. James has played in eight games on the second night of a back-to-back this season. In them, Cleveland’s offensive rating is a pathetic 100.1 when he's on the floor, and his True Shooting percentage is 54.5.

Juxtapose those numbers with the 33 games he's played with one or two days of rest before, and we begin to see that LeBron might be slowing down. On those nights his offensive rating is around 115 (that’s...elite) and his True Shooting percentage climbs 10 points.

Essentially, when James has time to relax he's about as efficient as Kyle Korver. When he doesn't, he's Mario Hezonja. Most of this is due to a gap in his three-point percentage, which is dreadful on the tail end of a back-to-back and otherwise above 40 percent.

For anyone else this isn’t news: Rest = Beneficial! But throughout his career, particularly since he re-joined the Cavaliers, it’s a law that hasn’t applied to LeBron. He was superhuman in a dozen games played on the second night of a back-to-back last season, dominating even more so than when he had a day or two off to recuperate. Cleveland’s offense was a force with him on the floor and he was never more accurate beyond the arc.

In 2016, Cleveland’s offense as a whole was noticeably worse without any rest, but James’s individual numbers didn’t suffer all that much compared to previous seasons. Go back to what’s arguably his pinnacle as a member of the Miami Heat, and LeBron was Arnold Schwarzenegger circa 1984-1987 on the second night of a back-to-back, pummeling the schedule into submission, exhibiting zero fall-off regardless of what stood in his team’s path. Everything is different this year.

Right now, the Golden State Warriors are 7-2 and +60 on the second night of a back-to-back. The Boston Celtics are -15 with a 5-3 record. The Houston Rockets are 3-3 and -10. The San Antonio Spurs are 6-4 and +18. The Toronto Raptors are 3-3 and +25. In other words, every team that has at least a puncher’s chance of winning the title is .500 or better in these tough conditions.

Meanwhile, the Cleveland Cavaliers are 3-5 with losses against the Orlando Magic, Brooklyn Nets, New York Knicks, Celtics, and Indiana Pacers. In those eight contests they’ve been outscored by 36 points.

There are a few explanations for this. Nearly all of them came without Isaiah Thomas on the floor and a few didn't feature Tristan Thompson (a 6’9” shot of espresso who helps erase fatigue). Most of Cleveland's new faces are also, well, pretty old. Dwyane Wade, Jeff Green, and Jose Calderon aren’t the difference-makers James is used to having by his side.

It all might've come to a head during a recent loss against Indiana, in which James played 40 minutes one night after a humiliating blowout loss to the Kyle Lowry-less Toronto Raptors. LeBron’s burst in the second half was noticeably lesser on both ends compared to the first two quarters. Watch how intense he is here denying the ball from Bojan Bogdanovic.

And here, one step ahead of his opponent as a weak-side defender, James perfectly times his rotation to disrupt Darren Collison’s entry pass and steal the ball.

Compare that focus to what happened on the third quarter’s very first possession. Domas Sabonis rolls into the paint and catches the ball at the free-throw line. He looks to his left and notices Victor Oladipo is tightly covered by J.R. Smith, sees Thaddeus Young is guarded down low, and then finds Bogdanovic wide open in the opposite corner.

James overhelps in the paint (after Love recovers back to Sabonis, Jae Crowder should drop back down to guard Young, or vice versa) and then doesn’t even take a step towards his man, who’s shooting 40 percent on wide open threes this season. Not great.

But the most disturbing slide has come in an area where he normally reigns supreme: the rim. James’ field goal percentage inside the restricted area is still an absurd 72.1 percent on the second night of a back-to-back, but it soars to 78.6 and 78.9 percent when he has one and two days off, respectively.

Here’s a play specifically designed to clear one side of the floor and provide LeBron with a runway to attack. It’s a misdirection that starts with Crowder and Love pretending to set a stagger screen for Calderon on the right side of the floor.

But once the Pacers shift over to defend it, Calderon whips the ball back to James, where all he has to do is get by Bogdanovic. It doesn't end as it should. Here are a couple more examples from the same night.

The percentage of LeBron's shots at the rim goes up by about six percent when he's not playing on the second night of a back-to-back, too. Instead of attacking Al Jefferson with a straight left-hand line drive (which he successfully pulled off earlier in the same game), here's a play where James snakes back to his right, fails to turn the corner, then settles for a contested step-back along the baseline.

This is obviously just one game in the middle of a long regular season. James still exists within the 0.1 percent of the top 0.1 percent athletes in the world, no matter who he’s playing, what day it is, or what he did to his body during the previous 24 hours. But it also reminds us that he’s an aging human being who’s no longer the tireless rhinoceros we’re used to. That sounds like pretty good news for the rest of the Eastern Conference.

Even though we've never seen him "struggle" like this before, LeBron (and the Cavaliers) will have a day or two off between every game throughout the playoffs. That means, for at least one more run, the NBA still has to go through King James. Anyone who watched him recover to pin Kevin Durant's layup against the backboard on Martin Luther King Jr. Day knows his athletic ceiling is still ridiculous enough to alter a game. But for the first time in well over a decade, the 13-time All-Star is beginning to reveal the type of slight imperfections that almost make him look mortal.